1. Field of the Invention
The present invention relates to a laser apparatus which is used to treat a diseased part of a patient by irradiating a treatment laser beam emitted from a laser source to the part to be treated.
2. Description of Related Art
Conventionally, there have been known laser apparatus which emit a treatment laser beam to the fundus of a patient's eye, thereby photocoagulating a part to be treated. A laser source used for such the laser apparatus excites and produces a laser beam in a laser tube. The light beam is reflected by a pair of mirrors (a reflection mirror and an output mirror) disposed in parallel and opposite to each other on both sides of the laser tube to resonate between the mirrors. Thus, a laser beam oscillation is ensured. In this case, if the setting angle of the reflection mirror deviates even a little from the proper angle, the mirror could not oscillate and emit laser beams or would reduce laser oscillating efficiency. This may cause inconveniences such as a lowering in output power of laser beams as compared with a setting power level. For solving the above problem, conventionally, the laser apparatus, upon turning the power thereof on, starts laser oscillation for an initial setting and drives the reflection mirror to rotate at the same time, thereby to measure the output power of laser beams during the rotation of the mirror. Based on the measurement results, the reflection mirror are adjusted to the angle where the highest laser oscillating efficiency can be obtained. An optimum laser oscillation can be ensured accordingly.
However, the above measurement of laser output power for an optimum laser oscillation is made by rotating the reflection mirror by every predetermined pulse, thereby taking a very long time and keeping an operator waiting for completion of the measurement.
In addition, the measurement, needing a long time, causes an increase of the consumption of electricity in the laser apparatus. As a result, the amount of heat generated is increased, resulting in a rise in temperature in the laser apparatus. This causes a problem that the temperature in the laser apparatus tends to come faster to the previously set upper limit of temperature where the laser apparatus can be operated. Especially, a laser treatment apparatus used for surgical operations would stop operating when the upper limit temperature is reached during the surgical operation. To prevent the stop of the apparatus, there is desired the laser apparatus capable of reducing the amount of heat generated therein to a minimum.